Electric-circuit breaker



(No Model.)

` BTHOMSON. yELECTRIC CIRCUIT BRBAKER. No. 490,178. v

Patented Jan. 17, 1893.

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UNITED STATES PATENT OFFICE.

ELIIIU THOMSON, OF SVAMPSCOTT, MASSACHUSETTS, ASSIGNOR T0 THE GENERALELECTRIC COMPANY, OE NEW YORK.

ELECTRIC-CIRCUIT BREAKER.

SPECIFICATION forming part of Letters Patent No. 490,178, dated January17, 1893. Application led October 28, 1892. Serial No. 450.223. (Nomodel.)

To all when@ it may concern:

Be it known that I, ELIHU THOMSON, a citizen of the United States,residing at Swampscott, county of Essex, and State of Massachusetts,have invented a certain new and useful Improvement in Electric-CircuitBreakers, of which the following is a specification.

The presentinvention relates to switches or other circuit controllingapparatus by means of which electric currents of great strength can besafely controlled. It is well known that difficulty is experienced inswitching currents of large volume, particularly when the potential isconsiderable. In such cases it is desirable that such circuit breakingapparatus be employed having contacts arranged to form multiple pathsthrough which the current is divided, but if on opening such a circuitthe time of make and break at the respective contacts is not absolutelysimultaneous the last one which is opened receives the full discharge ofthe heavy current and is apt to be injured. In this Way switches forheavy currents are very frequently damaged if the total volume ofcurrent is free to shift from one contact to another and so concentratethe entire current energy upon the one last opened. It is to obviatethis difculty that my invention is designed, and it may be applied toswitches and all forms of circuit breakers or controllers in whichshifting connections are to be made.

The accompanying drawings illustrate diagrammatically the inventionapplied in a number of its simplest forms, but it will be understoodthat I do not intend to restrict the invention to the particular form ofapparatus shown, or indeed to any particular form of circuit controller.

The principle on which the invention is founded is that currents willnot instantly leave circuits of considerable self-induction to seekother paths, and in applying this principle to the purpose in hand Iplacerin circuit with each of the multiple contacts a'self-inductivecoil or other device such that under normal conditions ypractically noimpedence is offered to the iiow of current, but which when the switchis opened maintains the proper distribution of the current through therespective paths so that only the proper fraction of the current isbroken at each of the contacts, for example, if each contact carries onehundred ampres and there are in all ten contacts at which the circuit isopened as nearly simultaneously as possible, then the amount of currentruptured by each contact will remain practically one hundred ampresinstead of one thousand ampres at the last of the contacts opened, aswould be the case in the ordinary multiple switch, for, as will bereadily understood, the increased current tending to rush through thelast contact gives rise to an electro-motive force `momentarily reducingthe iiow of increased current and preventing its passage during theshort interval during which the last contact remains closed after theothers have been lhpened.

In lthe drawings I have shown an ordinary self-inductive coil as thebest means for impeding the sudden shunting of the current from onecontact to another. In certain cases other devices accomplishing thesame function may be used.

In Figure l aknife switch is shown in which the moving member or blade Kis pivoted at a to a post P connected to one side of the circuit F. Theblade K engages when closed a number of stationary contacts A, B, C, andD which are connected in multiple to the other side of the circuit F,and are so arranged that when the blade is lifted the circuit would besimultaneously broken at the different contacts were it not forunavoidable errors of construction which make an absolutely simultaneousbreak difficult of attainment and not to be relied upon. The contacts A,B, C and D are connected together into a common line F by coils E, E',E2, E3, which are wound upon iron cores and have a certain self-induction depending upon the current which is to be opposed. Now assuming theswitch closed, a fraction of the entire line current will pass througheach of the contacts, and the different self-inductive coils. If theswitch be ysuddenly opened and the circuitaone or more contacts bebroken later than at the others, the self-inductive effect of the coilsE, E', E2, E3, will nevertheless preserve substantially that value ofcurrent through each of the contacts which was previously flowingthrough it, and thereby sudden concentration of the energy at one oranother of the contacts is avoided.

In Fig. 2 a modification of the invention is shown in which a pair ofcontacts A, B are connected respectively to line F through coils E5, E6wound reversely on the same core or around the same axis so as tonormally exert a counter magnetizing effect upon one another and therebynot impede the normal flow of current when the circuit is closed throughthe other contact K connected to line F. Should, however, in opening theswitch contact A or B leave K slightly before the other, an inductiveeffect due to an attempted shifting of the current to the contactremaining closed and through the corresponding reactive coil willmaintain the proper distribution of current as already described. Therewill be no magnetism developed by the coils E5, EG when there is anequal .division of current through them, but the moment a shifting tendsto take place such that the coil E, for example, receives the heavieriiow it magnetizes the core which acts independently7 to produce anelectro-motive force in the adjacent coil tending to force the currentto continue its original direction and allowing opening of theswitchwithout either contact carrying an undue fraction of the current- Thecoils E5 and EG may be wound upon a magnetic core of the open or closedmagnetic circuit type, Fig. 5 differing from Eig. 2 in showing a ringcore.

In Fig. 3 a slightly different form of switch apparatus is illustratedin which the contacts are designed to be opened and closed successivelyrather than simultaneously, and the reactive effect in each of themultiple paths is graduated correspondingly. The switch arm K carriescontacts A', B', O', D' and E'l adapted to engage the other linecontacts shown, and there is a clear connection between the contacts A,A without any intermediate coils, which contacts are the first openedand the last to be closed. The remaining contacts are also opened andclosed in succession, one after another, and in circuit with themrespectively are reactive coils E, E', E2, E3 constructed to give agraduated self-inductive et`fect,the coil E being of greater length andof greater self-induction than E' and the others arranged in likeprogression. In this way an increasing self-induction will be interposedin the paths remaining closed longest, and the circuit will be brokengradually at each of the contacts without any undue rush of current toany one as is the case with the other devices previously described.

Fig. 4 is a diagram of a double-pole switch making use of the invention.As indicated by the arrows the current enters at F and divides betweenthe two coils shown reversely wound on core I. Each of these divisionsis again redivided through similar coils wound on the cores J and L andlead eventually to a row of multiple contacts A, B, C and D. The othermember of the switch is shown at S and carries corresponding contactsA', B', O' and D connected to the other side of the circuit M. Thereturn circuit entering at N and leaving the switch at R is acounterpart of that described. In this last extension of the inventioneach pair of contacts as A-B or O-D are connected together through tworeversely wound coils, and the pairs themselves are similarly connectedthrough the coils on the core I. The inductions in the various coilswill, when the switch is thrown with moderate quickness insure a fairlyuniform division of current at the various contacts so that the properamount only is ruptured at each.

W'hat I claim as new and desire to secure by Letters Patent is.

l. The combination of amultiple contact circuit breaker' withself-inductive coils as described, arranged to preserve a properdistribution of the current between the different paths provided for it.

2. The combination of a multiple contact circuitbreaker with means forimpcding or rctarding the sudden rush of increased volume of currentthrough the contact or contacts which may be opened last.

3. The combination of a multiple circuit breaker with generators ofelectro-motive force acting upon a sudden increase of current throughany one path to retard such increased flow and maintain the normaldistribution of current, as described.

4. The combination ofa circuit breaker having multiple contacts, withconducting paths of considerable self-induction leading to such contactsrespectively and acting to preserve the proper distribution of currentflowing therethrough when the circuit is opened.

5. The combination of a circuit breaker affording multiple paths for thecurrent, with counter magnetizing or reversely wound selfinduction coilsin the respective paths so that the self-inductive effect is developedonly when the normal distribution of current bctween the different pathsis disturbed, as set forth.

6. The combination of a circuitbreaker affording multiple paths for thecurrent, which pathsare divided into pairs, countermaguetizing orreversely wound reactive coils normally balancing the self-inductiveeffect in each such path, and similar reactive coils through whichdifferent pairs are connected together, having a like normal countermagnetizing effect, as set forth.

7. An electric switch having multiple contacts connected togetherthrough self-inductive coils or devices impeding the instantaneousshifting of the current from one to another ofsuch contacts.

In testimony whereof I have hereto set my hand this 25th day of October,1892.

ELII-IU THOMSON.

Witnesses:

JOHN W. GIBBONEY, BENJAMIN B. HULL.

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